Firing mechanism



1943. N. K. TURNBULL ET AL 2,331,942

FIRING MECHANISM Filed Dec. 5, 1940 INVENTORS N lav-T111111. K-Tuv-nbull H ch21. 5111.1 11 QA M J W ATTORNEYS Patented Oct. 19, 1943FIRING MECHANISM Norman K. Turnbull, Pitman, N. 1., and Herschel Smith,Southampton, Pa.

Application December 1940, Serial No. 368,652

1 Claim. (01. its-341V (Granted under the act of March 3, 1883, as

amended April 30, 19.28; .37!) 0. G. 757) The invention described hereinmay be manufactured and used by or for the Government for governmentalpurposes, without the payment to us of any royalty thereon.

This invention relates to automatic firearms generally, and inparticular to a trigger motor synchronized with an aeroplane motor topermit firing between the blades of a propeller. of the general typeshown in U. S. Patent No. 1,450,653.

The invention consists in a trigger motor for attachment to the sideplate of a machine gun, said trigger motor having a plunger reciprocatedby an electromagnet andreturn spring and operating in a direct line onthe sear of the gun through a trip oif device, and wherein the plungeris adjustable in the direction of its motion.

It is an object of the invention to provide a trigger motor forautomatic firearms that will be compact and quick and dependable inoperation.

It is a further object of this invention to provide a trigger motor forautomatic firearms hav ing an electromagnet plunger with adjustableposition.

It is a further object of the invention to provide a trigger motorwherein the electromagnet plunger acts in a direct line on the sear.

To these and other ends, the invention consists in the construction,arrangement and combination of elements described hereinafter andpointed out in the claims forming a part of this specification.

A practical embodiment of the invention is illustrated in'theaccompanying drawing wherein:

Figure 1 shows a top view in axial section of the trigger motor asmounted on the left side of a gun, and

Figure 2 is a side view.

Referring to the drawing by characters of reference there is shown abase l of the trigger motor clamped to the side plate 2 of a machine gunby means of bolt 3 the head 4 of which nests in a conical seat in theside plate. The other end of the motor is held to the side plate in adovetail fit as at 5.

Bolted to the base I and fitted on an annular shoulder 6 of the base isa cylinder 1. This cylinder has diametrically opposite portions removedby milling as shown at 8 and $3 to an extent to penetrate the innersurface of the cylinder.

Fixed to cylinder 1 by means of screws it is a cover plate ll, and fixedcentrally thereof by means of screws I2 is a washer-like retainer l3 forthe spring I4.

Centrally of the cover H is a hub-like portion l5 slotted as at I 6forming'a sleeve seat for a jacket l! of the plunger assembly.

insulation on which the coil I8 is wound consists of a disk l9 restingon the base i, another disk 29' under the cover plate I l and acylindrical part 2! surrounding at its outer extremity the hub l5 and,at its inner extremity, an annular shoulder 22 on' the base I.

The plunger assembly consists of a central rod member 23 and jacketmembers i! and 24. Jacket 24 is fitted in a counterbore 2E iii-jacket i1and each jacket has an internal bore 26 threaded to receive a threadedenlargement 21 on rod 23. Jacket 24 has a flanged head '28, knurled orpolygonal and may be turned relative to jacket I! to lock rod 23 inposition. For this purpose, inner jacket ll is held against rotation bymeans of pins 29 engaging in slots l6.

Transmission of the thrust of plunger rod 23 to the sear 39 isaccomplished through the agency of a system of levers comprising a mainlever 3i pivoted by a pin 32 in a slot as in the base I, and a trip cfilever ea pivoted near the extremity of lever 3| by a pin 35.

Seated in the end of plunger rod 23 is a button headed screw 36afiording tangential contact with face 3'5 of the lever 3| as the latterswings under urging of the plunger rod 23. This swinging is resisted bya fiat spring 38 engaging main lever 3i. Both spring 33 and coiledspring it held between retainer l3 and flange 23 on outer jacket 2tserve to hold the plunger system normally retracted when the coil is isnot energized.

Trip-ofi 3 consists of a generally sectorshaped member having thinportions 22 and 43 and intermediate thickened portions J5 forming a pairof shoulders. Thin portion 82 is fitted in a slot 45 in lever 3i, andshoulders it serve to engage slant portions it on the sides of slot 45to form a stop for the trip-ofl (it, which is urged to this position bya flat spring Al retained in the lever 3! by a screw 40.

Shown at 48 is a lead-in plug for the wire 49, and attached to the fiatportion 8 of cylinder 1 by screws 50 is a housing for the plug socket 51consisting of a front plate 52 and side plates 53. Socket 5! is inelectrical connection with coil l8 and the terminus of the coil is ledout through an opening 54 in the cylinder '1 and grounded on thecylinder by means of a screw as at 55.

The wire 69 leads to an intermittent contact device functioning from anaircraft engine which is so adjusted as to energize the coil l8 onlywhen an opening between the propeller blades is in front of the gun.Such a contact device is :old in theart and is not hereillustrated sinceit forms no part of the present invention. For the same reason the searmechanism is not illustratecl, it'being sufiicient for the purposes ofthe present application to state that a sliding motion of the sear slide30 will result in release of the firing pin not shown).

The provision of a. coil seated on the base of the trigger motor makesfor compactness, and

The operation is as follows: Upon energization of the coil, the plungersystem 23, 24 and 11 or composite plunger moves inward as a unit tcompressing spring M and. forcing lever '31 inward against the pressureof spring 38. This motion is transmitted to sear slide 3l! through Itrip-off 34.

Upon firing, the bolt 56 is thrown -rearWar-d-1y,

carrying with it the sear slide 30, and is then the direct linear actionof the plunger on the sear slide speeds up the action. The generalfidelity of operation is improved by the adjustment feature on theplunger rod. t a

We claim:

"A trigger motor for anautoniatic gun, comprising 'abase having acentral Opening therein andadapted to be secured to theside plate of agun, a cylindrical sleevesecured to said base in I coaxial relation withsaid central opening, a

returned to battery position, the sear slide meanwhile being returnedtoits prefiring position, the

i position shown; in the t drawing. During I recoil and return of thebolt and sear, the plunger eontinues to reciprocate under the influence.of the I springs M ancl38 and the inte mittentenergization of the.0011. v I If the plunger system happens to be drawn iii- I wardly atthe time therboltreturns to battery, the

cover secured to the end of the cylinder and having a hub-like centralportion extending partway into said cylinder, an electromagnetic coilsurrounding said cylinder, a plunger reciproeable in said hub-likeportion and capable of completing amagnetic circuit to said base whensaid coil is energized, said plunger comprising a centrally "recessedinternally threaded portion extending through the hubalike portion, an

internally threaded flanged luck nut extending into said centrallyrecessed portion, a threaded returned sear slide will rotate thetrip-off :34

.sear slide will be waged inward to fire the next round. Thus, the gunwill always fire on the stroke of the plunger next succeeding the returnof the bolt to hatteryposition;

full 4 against the-pressure of its spring 41, thus permitting the boltto return to full battery position.

On the subsequent inward thrust of the plunger,

7 trip-off 34 will have returned to position against stop 46 under theurging of spring 41 and the rod engaging the threads of the lock nut andthreads of said centrally recessed portion and projecting through thecentral opening in the base; a centrally apertured'retainersecured tosaid cover for retaining the plungerin thecover, "a compression springinterposed between said retainer and lock nut flange, andvapmeans forlocking the plunger against rotation in said hub like portion NORMAN K.I

HERSCHELfiMITH.

